So I decided to pay the price and buy this ultimate shield that seemed much stronger and I had read a quick review on the site of a blogger.
Result: proceeds received within days. I unpack, remove my old backup, quickly clean my screen with the included cleaning wipe, and installs this new protection within seconds. No bubble has formed (honestly is the first time I see that). Only one or two grains of dust remained, but that's my fault.
Overall a very good product that deserves its price.